1. Technical Field
The present invention relates to a fluid passage structure, especially to a fluid passage structure having a crossing portion through which two flow passages cross with each other.
2. Description of Background Art
Conventionally, a high pressure joint like an L-shape joint, a T-shape joint, or a cruciform joint has a crossing portion through which two flow passages cross with each other. This joint is a joint through which a highly pressurized fluid supplied via a high pressure pump can be supplied to a prescribed portion after the flow of the highly pressurized fluid is bent, joined up, branched off or so on at the joint. The high pressure joint is widely used in a various jetting device for jetting a highly pressurized fluid or the like. Changing pressure (internal pressure) due to the highly pressurized fluid flowing in the flow passage repeatedly acts on the crossing portion of the high pressure joint. Consequently, it is known that a crack caused by the internal pressure affects seriously on the life of the joint (for example, refer to the patent literature 1).
In a high pressure joint described in the patent literature 1, compressive force is concentrated at positions directly over and directly under a crossing portion through which an X-axis flow passage and a Y-axis flow passage, which are formed on the same plane (X-Y plane) in the main body, cross with each other. Thereby, a Z-axis directional separating force (internal tensile stress) to act in the Z-axis direction orthogonal to the X-Y plane to force the main body to separate in the Z-axis direction is offset with the compressive force, so that a crack which may be caused in the X-Y plane is prevented.
Specifically, in the high pressure joint described in the patent literature 1, fixed compressive force is given to the crossing portion by fastening the main body via a first and a second compression members fastened with a fastening tool.
Patent literature 1: Japanese Unexamined Patent Publication (Translation of PCT Application) No. 2008-510937 (claims 1, 2, paragraphs 0018 to 0020)